package network;

import java.io.IOException;
import java.net.*;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Microsoft
 * Date: 2023-08-01
 * Time: 17:47
 */
public class UdpEchoClient {
    private DatagramSocket socket = null;
    private String serverIp;
    private int serverPort;

    //客户端启动，需要知道服务器在哪里
    public UdpEchoClient(String serverIP,int serverPort) throws SocketException {
        //对于客户端来说，不需要显示显示关联端口
        //不代表没有端口，而是系统自动分配了一个空闲的端口
        socket = new DatagramSocket();

        this.serverIp = serverIP;
        this.serverPort = serverPort;
    }

    public void start() throws IOException {
        //通过这个客户端，可以多次和服务器进行交互
        Scanner scanner = new Scanner(System.in);
        while (true) {
            // 1. 先从控制台，读取一个字符串过来
            System.out.print(" -> ");//先打印一个提示符，提示用户要输入内容
            String request = scanner.next();


            // 2.把这个字符串构造成UDP packet，并进行发送
            DatagramPacket requestPacket =  new DatagramPacket(request.getBytes(),request.getBytes().length,
                    InetAddress.getByName(serverIp),serverPort);
            socket.send(requestPacket);


            // 3. 客户端尝试读取服务器返回的响应

            DatagramPacket responsePacket = new DatagramPacket(new byte[4096],4096);//构造一个空的对象，作为接收
            socket.receive(responsePacket);
            // 4. 把响应数据转换成String显示出来
            String response = new String(responsePacket.getData(),0,responsePacket.getLength());
            System.out.printf("req : %s, resp : %s\n",request,response);
        }
    }

    public static void main(String[] args) throws IOException {
        UdpEchoClient udpEchoClient = new UdpEchoClient("127.0.0.1",9090);//127.0.0.1是环回
        udpEchoClient.start();
    }
}


















